The invention relates to a coupling disc for a belt retractor of a vehicle safety belt.
A coupling disc normally has a coupling catch which is pivotally mounted thereon so as to be movable between a position of rest and a coupling position.
The coupling disc is a generally known component of a locking mechanism by which a belt spool of the belt retractor can be locked so that no more safety belt can be withdrawn from the belt retractor. For the sake of completeness, such a locking mechanism is briefly described below with reference to FIG. 1.
The belt retractor has a frame 10, in which a belt spool 12 is rotatably mounted. The belt spool 12 is provided on at least one axial end with locking teeth 14 into which a locking catch 16 can be guided. The locking catch is pivotally mounted on the frame 10. To move the locking catch, an actuating pin 18 is used, which engages into a recess 20 of the locking catch 16 and is securely arranged on a locking lever 22. The locking lever 22 is pivotally arranged on the frame 10 turning about the same central axis C as the belt spool 12. The locking lever 22 is biased by a restoring spring 24 into the position of rest shown in FIG. 1, in which the actuating pin 18 holds the locking catch 16 in its position of rest, in which it does not engage into the teeth 14 of the belt spool 12. If, on the other hand, the locking lever 22 is rotated in the direction of the arrow A, i.e. clockwise with respect to FIG. 1, it guides the locking catch 16 into the locking teeth 14 of the belt spool 12 by means of the actuating pin 18. The belt spool is then locked against a further rotation in the direction of the arrow A, i.e. in the belt band withdrawal direction.
The rotation of the locking lever 22 for the purpose of locking the belt spool is brought about by a rotation of the belt spool 12 in the belt band withdrawal direction, this rotation being firstly transferred to a coupling disc 26 which is connected with the belt spool 12 for joint rotation therewith, and from this disc to the locking lever.
When the locking mechanism of the belt retractor is activated in a belt band-sensitive manner, i.e. when the angular acceleration of the belt spool 12, brought about by the belt band, exceeds a predetermined value, then a coupling catch 28 pivotally mounted on the coupling disc 26 is rotated out from its position of rest into a coupling position, in which it engages into coupling teeth 29 on the locking lever 22. A conventional inertia disc (not illustrated in FIG. 1) may be used for pivoting the coupling catch 28. When the coupling catch 28 is in its coupling position, a rotation of the belt spool is transferred via the coupling disc 26, connected to the spool for joint rotation therewith, the coupling catch 28 arranged on the coupling disc, and via the coupling teeth 29 to the locking lever 22 which is entrained in the direction of the arrow A. In this way, the actuating pin 18 arranged on the locking lever 22 can guide the locking catch 16 into the locking teeth 14 of the belt spool 12.
When the locking mechanism is triggered in a vehicle-sensitive manner, i.e. by exceeding an acceleration or deceleration acting on the vehicle and hence also on the belt retractor, a conventional inertia sensor (not illustrated) swivels an entrainment lever 30 from the position of rest shown in FIG. 1 into an active position in which it engages into entrainment teeth 32 provided on the coupling disc 26. The entrainment lever 30 is mounted on the locking lever 22 so that a rotation of the belt spool in the belt band withdrawal direction is transferred via the coupling disc 26, the entrainment teeth 32 and the entrainment lever 30 to the locking lever 22, whereby the locking catch 16 is guided by the actuating pin 18 into the locking teeth 14 of the belt spool 12.
With the belt band-sensitive engaging of the locking mechanism, it is important that the values of the angular acceleration are reproducible, at which the locking mechanism responds. For safety reasons, specific values must not be fallen below. If, however, the locking mechanism responds unnecessarily early, this can lead to the locking mechanism already responding when the safety belt is put on normally, but somewhat jerkily. This is generally felt to be unpleasant.
The object of the invention consists in providing a coupling disc by which as precise a response of the locking mechanism as possible is ensured.
According to the invention, a coupling disc for a belt retractor of a vehicle safety belt comprises a coupling catch which is pivotally mounted on the coupling disc so as to be movable between a position of rest and a coupling position. The coupling catch and the coupling disc are formed in one piece from plastic. A hinge section is provided between the coupling catch and the coupling disc. The invention is based on the knowledge that the engaging parameters of the locking mechanism are most able to be reproduced if the friction which acts between the parts then moving on engaging of the locking mechanism is avoided as far as possible. In contrast to the prior art, in which usually the coupling catch is mounted on a pin on the coupling disc, according to the invention a type of film hinge or a spring is provided. Apart from a negligible internal material friction, which takes place with a bending of the hinge section, the coupling catch is arranged so as to be free of friction on the coupling disc. The inherent elasticity of the hinge section, furthermore, has the advantage that a restoring spring for the coupling catch may possibly be dispensed with; a restoring spring also produces friction in the system. Furthermore, advantages are produced as regards the installation and the production costs. The coupling catch does not need to be produced, provided and installed as a separate component, but rather is automatically produced on manufacture of the coupling disc as a part connected in one piece therewith. In this way, in addition, any risk of faulty installation is eliminated. A further advantage consists in that with the manufacture in one piece, the otherwise unavoidable tolerance fluctuations are eliminated. The hinge section may be adapted in a simple manner to the respective requirements by its cross-section being suitably selected. With a correspondingly small cross-section, the coupling catch can have such an easy action that no additional inertia disc is necessary for its actuation; it is rotated into its coupling position solely by the inertia- and centrifugal forces which act on it with a corresponding angular acceleration of the coupling disc.
According to a preferred embodiment of the invention, provision is made that the hinge section runs in a curved shape and has a rectangular cross-section, the longer direction of which runs parallel to the swivel axis of the coupling catch. In this way, a slight bending resistance is produced for the swiveling of the coupling catch between the position of rest and the coupling position, however a very much higher bending resistance against an xe2x80x9cundesiredxe2x80x9d deflection of the coupling catch transversely thereto.
Preferably, provision is made that the coupling disc has a support surface on which the coupling catch can rest when it is in the coupling position. As the hinge section can only transfer very small forces owing to its flexibility, the use of a support surface presents itself, in order to introduce the forces necessary for swiveling the locking lever on a short distance from the coupling disc via the coupling catch into the coupling teeth of the locking lever.
If no additional inertia disc is to be used for swiveling the coupling catch, provision is preferably made that on the coupling catch a weight element of metal is provided, for example a ball which is clipped into the coupling catch. In this way, the inertia- and centrifugal forces can be increased which in the case of an angular acceleration of the coupling disc act on the coupling catch and swivel the latter from the position of rest into the coupling position.
Alternatively, provision can be made that the coupling disc is provided with an inertia disc which has an actuation extension which can move the coupling catch into the coupling position. Also in this case, positive use is made of the small friction forces for the mounting of the coupling catch.
Preferably, provision is made that the inertia disc is provided with at least one stop extension and the coupling disc has at least one elastic damping element on which the stop extension can rest. The necessary delimitation of rotation of the inertia disc relative to the coupling disc is delimited by the stop extension together with the damping element, the elasticity of the damping element serving to entrain the stop extension of the inertia disc as gently as possible when the damping element of the leading coupling disc meets the stop extension of the still stationary inertia disc.
The coupling disc is preferably provided with at least one reinforcement rib. Such a reinforcement rib serves to prevent a possible distortion of the coupling disc. As the mounting of the coupling catch by means of the hinge section is very compact, a large number of reinforcement ribs can be provided on the coupling disc.
For an instance where the inherent elasticity of the hinge section is not sufficient to reliably restore the coupling catch to its position of rest, a restoring spring of metal is provided. This preferably consists of a spring wire having a round cross-section, because the spring characteristics of a spring wire with a round cross-section are subject to lower tolerances than those of a spring wire having a rectangular cross-section. The spring wire is preferably clipped simply into a groove on the coupling disc and lies against a holding nose of the coupling catch.
Two coupling catches may also be provided, which lie diametrically opposite each other. This is particularly advantageous when no restoring spring is used for the coupling catch, but rather merely the inherent elasticity of the correspondingly thinly dimensioned hinge section is used. In this case, the restoring force of the hinge section is expectedly so small that the influence of gravity on the coupling catch takes effect on the engaging behavior. Therefore the coupling catch, which with an installed belt retractor, according to rotation of the coupling disc, is in fact situated in the lower region of its path, i.e. in the xe2x80x9c6 o""clock positionxe2x80x9d, will be guided undesirably early into the coupling teeth of the locking lever, because this is supported by gravity. This can be counteracted by a stop being provided, fixed to the frame, on the belt retractor, which stop extends across a defined angular section along the lower region of the path of movement of the coupling catches. This stop prevents the one coupling catch which is then situated in the lower region of its path, from being rotated out of its position of rest into the coupling position and thereby already with an undesirably low angular acceleration of the belt spool leading to its locking. If the constructionally provided angular acceleration of the belt spool is reached, which is to lead to a locking, the opposite coupling catch, namely the one situated in the region of the xe2x80x9c12 o""clock positionxe2x80x9d is available for activation of the locking mechanism. If, on the other hand, the coupling disc is in a position in which the two coupling catches lying opposite each other are in the xe2x80x9c3 o""clock positionxe2x80x9d and the xe2x80x9c9 o""clock positionxe2x80x9d, both coupling catches are available.
According to one preferred embodiment provision is made that the hinge section is formed by a leaf spring which is embedded in the coupling disc and the coupling catch by injection-molding, so that the coupling catch is made in one piece with the coupling disc.
Advantageous developments of the invention will become apparent from the sub-claims.